Optical element and method for fabricating the same

ABSTRACT

An optical element and manufacturing method thereof are provided which, by preventing the incidence of light on unnecessary portions, can prevent the occurrence of stray light and noise. An optical element  21  is configured from one or more substrates comprising lens substrates  13, 14  in which are embedded lenses  11, 12  of material with higher refractive index than the substrates, and with shielding means  15  to limit the optical path such that incident light propagates only within a prescribed optical path formed on the light incidence-side or emission-side surface of one of the substrates  13, 14.  Also, an optical element  21  is manufactured having shield means through the formation of an absorptive or reflective film  15  in the region outside the prescribed optical path or through machining of the region outside the prescribed optical path, performed on the light incidence-side or emission-side surface of a substrate  13, 14.

TECHNICAL FIELD

[0001] This invention relates to an optical element comprising a lenssubstrate, in which a high-refractive-index lens is embedded in asubstrate, and a manufacturing method therefor.

BACKGROUND ART

[0002] Apertures are important components of optical pickups and otheroptical apparatuses which, by limiting the optical path, eliminatesstray light and other external disturbances.

[0003]FIG. 14 shows the conventional configuration of an optical headusing an optical element proposed in, for example, Japanese PatentApplication No. 2000-132897, Japanese Patent Application No.2000-189730, or similar.

[0004] This optical element (lens element) 70 is configured by stackinga first lens substrate 73, in which a first objective lens 71 isembedded in a transparent substrate, and a second lens substrate 74, inwhich a second objective lens 72 is embedded in a transparent substrate.

[0005] The first and second objective lenses 71 and 72 have higherrefractive indices than the respective surrounding transparentsubstrates.

[0006] By means of two lenses, which are the first objective lens 71 andthe second object lens 72, the light beam L converges and irradiates theoptical disc 80.

[0007] In the prior art, an aperture 75 to limit the optical path is,for example, formed from a collimating lens 76 or similar formed usingconventional manufacturing methods, as shown in FIG. 14. In theconfiguration of FIG. 14, the aperture 75 comprises a lens holder of,for example, black plastic or similar, which holds the collimating lens76.

[0008] However, for the configuration shown in FIG. 14, when for exampleaxis inclination of the optical path occurs due to motion in thehorizontal direction of the collimating lens 76, light may be guidedinto regions outside the effective area of the objective lenses 71 and72, and the guiding of light into the region within the effective areamay be prevented. As a result, stray light occurs, becoming lightreturning to the semiconductor laser or distorting the shape of thefocused spot of laser light, and as a result generating noise or causingother problems.

[0009] In order to resolve the above problems, this invention providesan optical element and manufacturing method thereof which enables theavoidance of stray light and noise, by preventing the incidence of lighton unnecessary portions and by ensuring that light is not prevented frombeing guided to the region within the effective area.

DISCLOSURE OF THE INVENTION

[0010] An optical element of this invention comprises one or moresubstrates which are transparent to incident light, each comprising alens substrate formed by embedding, in a substrate transparent toincident light, a lens of material with a higher refractive index thanthat of the substrate; one among the one or more substrates is formedwith shielding means, in the surface of light incidence or in thesurface of light emission, to limit the optical path such that incidentlight propagates only within a prescribed optical path through theaction of either reflection, refraction, absorption, or dispersion.

[0011] By means of the configuration of the above-described opticalelement of this invention, shielding means to limit the optical pathsuch that incident light propagates only within a prescribed opticalpath, through the action of either reflection, refraction, absorption ordispersion, is formed in the surface of light incidence or in thesurface of light emission in one substrate among the one or moresubstrates, so that it is possible through the shielding means to shieldlight such that light is not incident outside the prescribed opticalpath (for example, outside the effective region of the lens), that is,in unnecessary portions.

[0012] A method of manufacture of an optical element of this inventionis a method of formation of an optical element comprising one or moresubstrates, transparent to incident light, each comprising a lenssubstrate formed by embedding, in a substrate transparent to incidentlight, a lens of material with a higher refractive index than that ofthe substrate; having a process of formation, in one among the one ormore substrates, of an absorption or reflection film in the regionoutside a prescribed optical path in the surface on the incidence sideor on the emission side of the substrate.

[0013] A method of manufacture of an optical element of this inventionis a method of formation of an optical element comprising one or moresubstrates, transparent to incident light, each comprising a lenssubstrate formed by embedding, in a substrate transparent to incidentlight, a lens of material with a higher refractive index than that ofthe substrate; having a process of machining, in one among the one ormore substrates, a region outside a prescribed optical path in thesurface on the incidence side or on the emission side of the substrate.

[0014] By means of the above-described methods of manufacture of anoptical element of this invention, by forming an absorption orreflection film in a region outside a prescribed optical path, or bymachining a region outside a prescribed optical path, in a surface onthe incidence side or on the emission side of a substrate, shieldingmeans employing an absorption or reflection film or employing machiningcan be formed in a region outside the prescribed optical path in thesurface.

[0015] Through the shielding means, the optical path can be limited suchthat light is not incident in unnecessary portions outside theprescribed optical path.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 is a cross-sectional view in summary of the configurationof major portions of an optical head using an optical element of thisinvention;

[0017]FIG. 2 is a cross-sectional view in summary of the configurationof major portions of an optical head using an optical element of thisinvention;

[0018]FIG. 3 is a cross-sectional view in summary of the configurationof major portions of an optical head using an optical element of thisinvention;

[0019]FIG. 4A to FIG. 4C are drawings showing optical elements in formsin which a rough surface is formed in the surface on the incidence sideor on the emission side of the lens substrate;

[0020]FIG. 5 is a cross-sectional view in summary of the configurationof major portions of an optical head using an optical element of thisinvention;

[0021]FIG. 6A to FIG. 6C are drawings showing forms of optical elementsof this invention in which the light incidence-side surface of the firstlens substrate is machined to form an aperture;

[0022]FIG. 7A to FIG. 7C are drawings showing forms of optical elementsof this invention in which the light emission-side surface of the firstlens substrate is machined to form an aperture;

[0023]FIG. 8A to FIG. 8D are drawings showing forms of optical elementsof this invention in which the light incidence-side surface of thesecond lens substrate is machined to form an aperture;

[0024]FIG. 9A to FIG. 9C are drawings showing forms of optical elementsof this invention in which the light emission-side surface of the secondlens substrate is machined to form an aperture;

[0025]FIG. 10A to FIG. 10D are process diagrams showing processes tomanufacture an optical element with the configuration of FIG. 1;

[0026]FIG. 11A to FIG. 11D are process diagrams showing processes tomanufacture an optical element with the configuration of FIG. 4A;

[0027]FIG. 12A to FIG. 12E are process diagrams showing processes tomanufacture an optical element with the configuration of FIG. 6A;

[0028]FIG. 13 is a cross-sectional view showing a form of an opticalelement configured from one objective lens; and,

[0029]FIG. 14 is a cross-sectional view showing a conventionalconfiguration of an optical head using an optical element comprising twolens substrates.

BEST MODE OF CARRYING OUT THE INVENTION

[0030] This invention relates to an optical element comprising one ormore substrates which are transparent to incident light, each comprisinga lens substrate formed by embedding, in a substrate transparent toincident light, a lens of material with a higher refractive index thanthat of the substrate; one among the one or more substrates is formedwith shielding means, in the surface of light incidence or in thesurface of light emission, to limit the optical path such that incidentlight propagates only within a prescribed optical path through theaction of either reflection, refraction, absorption, or dispersion.

[0031] The above-described optical element of this invention isconfigured by stacking a plurality of lens substrates.

[0032] A method of manufacture of an optical element of this inventionis a method of formation of an optical element comprising one or moresubstrates, transparent to incident light, each comprising a lenssubstrate formed by embedding, in a substrate transparent to incidentlight, a lens of material with a higher refractive index than that ofthe substrate; this method of manufacture of an optical element has aprocess of formation, in one among the one or more substrates, of anabsorption or reflection film in the region outside a prescribed opticalpath in the surface on the incidence side or on the emission side of thesubstrate.

[0033] A method of manufacture of an optical element of this inventionis a method of formation of an optical element comprising one or moresubstrates, transparent to incident light, each comprising a lenssubstrate formed by embedding, in a substrate transparent to incidentlight, a lens of material with a higher refractive index than that ofthe substrate; this method of manufacture of an optical element has aprocess of machining, in one among the one or more substrates, a regionoutside a prescribed optical path in the surface on the incidence sideor on the emission side of the substrate.

[0034] In the above-described optical element manufacturing method ofthis invention, a process of machining a region outside a prescribedoptical path is a process of forming a rough surface in the region.

[0035] In the above-described optical element manufacturing method ofthis invention, a process of machining a region outside a prescribedoptical path is a process of machining this region to become an inclinedsurface with respect to the region within the prescribed optical path.

[0036] In the above-described optical element manufacturing method ofthis invention, a process of machining a region outside a prescribedoptical path is a process of machining to form a groove with respect tothis region.

[0037] In the above-described optical element manufacturing method ofthis invention, a process of machining a region outside a prescribedoptical path is a process of forming an opening portion to open thisregion and the region within the prescribed optical path, such that thisregion is an inclined surface.

[0038] Prior to explaining specific aspects of this invention, first asummary of this invention is explained.

[0039] In this invention, an optical element is configured having one ormore substrates transparent to incident light, each comprising asubstrate transparent to incident light in which is embedded a lens ofmaterial with a refractive index higher than that of the substrate.

[0040] As a substrate transparent to incident light, if for example theincident light is visible light then an ordinary transparent substrateis used; if for example the incident light is in the ultraviolet regionthen a substrate which transmits light in the ultraviolet region isused; and if for example the incident light is in the infrared regionthen a substrate which transmits light in the infrared region is used.

[0041] As a lens substrate comprising a substrate transparent toincident light in which is embedded a lens of material with refractiveindex higher than that of the substrate, for example, a solid immersionlens (SIL) or similar is conceivable.

[0042] As the basic structure of the optical element of this invention,in addition to the structure of an ordinary solid immersion lens, forexample, previously proposed structures (Japanese Patent Application No.2000-132897, Japanese Patent Application No. 2000-189729, JapanesePatent Application No. 2000-189730, Japanese Patent Application No.2000-305122, Japanese Patent Application No. 2001-37366, or JapanesePatent Application No. 2001-51736) can be adopted.

[0043] In this invention, shielding means to limit the optical path suchthat incident light propagates only within a prescribed optical path, bythe action of either reflection, refraction, absorption, or dispersion,is provided on the incidence-side surface or on the emission-sidesurface of one substrate among the one or more substrates transparent toincident light in the above-described basic structure of the opticalelement.

[0044] Through this shielding means, a so-called aperture can beconfigured.

[0045] As a shielding means which employs reflection for shielding, forexample, formation of a reflective film, or alteration of the surfaceoutside the prescribed optical path to an inclined surface with respectto a surface (incidence surface or similar) within a prescribed opticalpath, are conceivable.

[0046] As a shielding means which employs refraction for shielding, forexample, alteration of the surface outside the prescribed optical pathto an inclined plane with respect to a surface (incidence surface orsimilar) within a prescribed optical path is conceivable.

[0047] As a shielding means which employs absorption for shielding,formation of an absorptive film is conceivable.

[0048] As a shielding means which employs dispersion for shielding,formation of a structure which causes dispersion of incident light onthe surface outside the prescribed optical path is conceivable; forexample, a rough surface may be formed, or a film with dispersive actionmay be formed.

[0049] By providing shielding means in this way, the optical path can belimited (shielded) such that incident light is not incident onunnecessary portions outside the prescribed optical path (for example,outside the effective region of the lens).

[0050] Hence the occurrence of stray light due to incidence of light onunnecessary portions can be prevented, and, for example, instability dueto light returning to a semiconductor layer as well as noise and similarproblems can be avoided.

[0051] Next, specific aspects of this invention are explained.

[0052]FIG. 1 is a cross-sectional view in summary of the configurationof major portions of an optical head using an optical element of thisinvention, as one aspect of this invention. This aspect is a solidimmersion lens (SIL) comprising a first objective lens 11 and secondobjective lens 12 as objective lenses, and shows a case in which theshielding means, that is, the aperture, is formed on the surface on thelight incidence side of the first objective lens 11.

[0053] The optical head shown in FIG. 1 comprises an optical element(lens element) 21 and a collimating lens 16; the optical element 21comprises the above-described solid immersion lens consisting of a firstobjective lens 11 and second objective lens 12.

[0054] The first objective lens 11 is formed embedded in a first lenssubstrate 13; the second objective lens 12 is formed embedded in asecond lens substrate 14.

[0055] The first and second objective lenses 11 and 12, and the firstand second lens substrates 13 and 14, are all formed from material whichis transparent to the incident light beam L.

[0056] Further, the first and second objective lenses 11 and 12 areformed from material having a higher refractive index than that of thefirst and second lens substrates 13 and 14.

[0057] In this aspect, an absorptive or reflective film 15 is formed inparticular on the surface on the side on which light is incident on thefirst objective lens 11 of the optical element 21, that is, on theincidence-side surface of the first lens substrate 13 in which isembedded the first objective lens 11, to form an aperture.

[0058] The absorptive or reflective film 15 forming an aperture is anabsorptive film formed from light-absorbing material or a reflectivefilm formed from light-reflecting material.

[0059] As an absorptive film, for example, a layered film in which adielectric film of silicon oxide or similar is formed to a prescribedthickness on top of a film of chromium or another metal, or a carbonfilm or other film with extremely low reflectivity, can be used.

[0060] As a reflective film, aluminum, gold, chromium, or anotherordinary metal or similar can be used. Because there is no need for aparticularly high reflectivity, tungsten or another material with lowreflectivity may be used.

[0061] In the above-described aspect, by means of the absorptive orreflective film 15 formed on the incidence-side surface of the firstlens substrate 13, a portion of the light in the optical path of thelight beam L is absorbed or reflected, so that the optical path of thelight beam L is limited, and operation as an aperture is achieved.

[0062]FIG. 2 is a cross-sectional view in summary of the configurationof major portions of another aspect of an optical head using an opticalelement of this invention.

[0063] An absorptive or reflective film 15 similar to that shown in FIG.1 is formed, either on the light emission-side surface of the first lenssubstrate 13 in which is embedded the first objective lens 11 or on thelight incidence-side surface of the second lens substrate 14 in which isembedded the second objective lens 12, to form the optical element (lenselement) 22.

[0064] In this configuration also, similarly to FIG. 1, an aperture isformed by the absorptive or reflective film 15.

[0065] Similarly to the configuration of FIG. 1, this aspect can alsooperate as an aperture limiting the optical path of the light beam L, byabsorbing or reflecting light in a portion of the optical path of thelight beam L by means of the absorptive or reflective film 15 formed oneither the light emission-side surface of the first lens substrate 13 oron the light incidence-side surface of the second lens substrate 14.

[0066]FIG. 3 is a cross-sectional view in summary of the configurationof major portions of another aspect of an optical head using an opticalelement of this invention.

[0067] An absorptive or reflective film 15 similar to that shown in FIG.1 is formed on the light emission-side surface of the second lenssubstrate 14 in which is embedded the first objective lens 12, to formthe optical element (lens element) 23.

[0068] In this configuration also, similarly to FIG. 1, an aperture isformed by the absorptive or reflective film 15.

[0069] In this case, the light beam L which has passed through the firstobjective lens 11 converges and is incident on the second objective lens12; on the other hand, the light beam L passing outside the firstobjective lens 11 of the first lens substrate 13 does not converge butpasses unchanged through the second lens substrate 14, and so this lightis separated at the emission-side surface of the second lens substrate14.

[0070] Consequently the absorptive or reflective film 15 need not beprovided up to the very outer edge of the second objective lens 12, butmay be provided at least in the range within which the light beam Lpassing through the outside of the objective lens 11 arrives.

[0071] Similarly to the configuration of FIG. 1, this aspect can alsooperate as an aperture limiting the optical path of the light beam L, byabsorbing or reflecting light in a portion of the optical path of thelight beam L by means of the absorptive or reflective film 15 formed onthe emission-side surface of the second lens substrate 14.

[0072]FIG. 4A to FIG. 4C are cross-sectional views showing still otheraspects of an optical element of this invention.

[0073] In any of these aspects, shielding means, that is, an aperture,is formed by forming a rough surface 17 on the incidence-side or theemission-side surface of the lens substrate 13 or 14.

[0074] In the optical element (lens element) 24 of FIG. 4A, a roughsurface 17 is formed on the light incidence-side surface of the firstlens substrate 13 in which is embedded the first objective lens 11, toform an aperture.

[0075] In the optical element (lens element) 25 of FIG. 4B, a roughsurface 17 is formed on the light incidence-side surface of the secondlens substrate 14 in which is embedded the second objective lens 12, toform an aperture. Similar action is obtained even if the rough surfaceis formed on the light emission side of the first lens substrate 13 inwhich is embedded the first objective lens 11.

[0076] In the optical element (lens element) 26 of FIG. 4C, a roughsurface 17 is formed on the light emission-side surface of the secondlens substrate 14 in which is embedded the second objective lens 12, toform an aperture.

[0077] In the case of FIG. 4C, for the same reason as with theconfiguration of FIG. 3C, the rough surface 17 need not be provided upto the very outer edge of the second objective lens 12, but may beprovided at least in the range within which the light beam L passingthrough the outside of the objective lens 11 arrives.

[0078] In these optical elements 24, 25 and 26, the rough surface 17forming the aperture has the property of dispersing light, and so bydispersing the light of a portion of the optical path of light incidenton the optical elements 24, 25 and 26, the optical path is limited, andthe action of an aperture is obtained.

[0079]FIG. 5 is a cross-sectional view in summary of the configurationof major portions of another aspect of an optical head using an opticalelement of this invention.

[0080] By cutting the surface of the first lens substrate 13 on thelight incidence side to obtain an inclined surface 18, an opticalelement (lens element) 27 in which is formed shielding means, that is,an aperture, is obtained.

[0081] In this optical element 27, the inclined surface 18 comprised bythe aperture reflects or refracts light incident on the inclined surface18. Consequently one portion of the light in the optical path of thelight incident on the optical element 27 is reflected or refracted bythe inclined surface 18 and is bent in a direction different from thedirection of the original optical path, and by this means the opticalpath is limited, and action as an aperture is obtained.

[0082]FIG. 6A to FIG. 6C are cross-sectional views showing still otheraspects of an optical element of this invention.

[0083] In all aspects, the shielding means, that is, aperture, isconfigured by machining the light incidence-side surface of the firstlens substrate 13.

[0084] In the optical element (lens element) 28 shown in FIG. 6A, thelight incidence-side surface of the first lens substrate 13 is machinedto form a V-shaped depression, that is, a groove 19, to form anaperture.

[0085] The V-shape groove 19 reflects or refracts light incident on theinclined surface. Consequently light in a portion of the optical path ofthe light incident on the optical element 28 is reflected or refractedby the side faces of the groove 19 and is bent in a direction differentfrom the direction of the original optical path, so that the opticalpath is limited and the action of an aperture can be obtained.

[0086] In the optical element (lens element) 29 shown in FIG. 6B, thelight incidence-side surface of the first lens substrate 13 is machinedto form two V-shaped depressions, that is, the grooves 19 (19A, 19B), toform an aperture.

[0087] The two grooves 19A, 19B are formed as dual grooves such that,for example, the centers coincide according to the cross-sectional shapeof the first objective lens 11. For example, if the cross-sectionalshape of the first objective lens 11 is circular, a concentric circularshape is formed. Further, the two grooves 19A, 19B are formedcontinuously in the horizontal direction without opening an interval.

[0088] In this case also, a portion of the light in the optical path ofthe light incident on the optical element 29 is reflected or refractedby the side faces of the two grooves 19A, 19B, bending the light in adirection different from the direction of the original optical path andlimiting the optical path, so that action as an aperture can beobtained.

[0089] In the optical element (lens element) 30 shown in FIG. 6C, anopening portion is formed by machining of the light incidence-sidesurface of the first lens substrate 13 with the side face shaped as aninclined surface 20, the first objective lens 11 with higher refractiveindex than the first lens substrate 13 is exposed, and an aperture isformed by the inclined surface 20 of the side face of the openingportion.

[0090] The inclined surface 20 of the side face of the opening portionrefracts or reflects incident light. Consequently a portion of the lightin the optical path of light incident on the optical element 30 isreflected or refracted by the inclined surface 20 and is bent in adirection different from the direction of the original optical path, sothat the optical path is limited, and action as an aperture is obtained.

[0091]FIG. 7A to FIG. 7C are cross-sectional views showing still otheraspects of an optical element of this invention.

[0092] In all aspects, the light emission-side surface of the first lenssubstrate 13 is machined to form shielding means, that is, an aperture.

[0093] In the optical element (lens element) 31 of the aspect shown inFIG. 7A, the light emission-side surface of the first lens substrate 13is machined to form a V-shape groove 19, to form an aperture.

[0094] In this case also, similarly to the aspect shown in FIG. 6A, aportion of the light of the optical path of light incident on theoptical element 31 is reflected or refracted by the side faces of theV-shape groove 19 and bent in a direction other than the direction ofthe original optical path, so that the optical path is limited, andaction as an aperture can be obtained.

[0095] In the optical element (lens element) 32 of the aspect shown inFIG. 7B, the light emission-side surface of the first lens substrate 13is machined to form two V-shape grooves 19 (19A, 19B), to form anaperture.

[0096] In this case also, similarly to the aspect shown in FIG. 6B, aportion of the light of the optical path of light incident on theoptical element 32 is reflected or refracted by the side faces of thetwo V-shape grooves 19A and 19B and is bent in a direction other thanthe direction of the original optical path, so that the optical path islimited, and action as an aperture can be obtained.

[0097] In the optical element (lens element) 33 of the aspect shown inFIG. 7C, the light emission-side surface of the first lens substrate 13is cut obliquely by machining into an inclined surface 18, and by meansof this inclined surface 18 an aperture is formed.

[0098] In this case also, similarly to the optical element 27 shown inFIG. 5, a portion of the light in the optical path of the light incidenton the optical element 33 is reflected or refracted by the inclinedsurface 18 and is bent in a direction other than the direction of theoriginal optical path, so that the optical path is limited, and actionas an aperture can be obtained.

[0099]FIG. 8A to FIG. 8D are cross-sectional views showing still otheraspects of an optical element of this invention.

[0100] In all aspects, the light incidence-side surface of the secondlens substrate 14 is machined to form shielding means, that is, anaperture.

[0101] In the optical element (lens element) 34 of the aspect shown inFIG. 8A, the light incidence-side surface of the second lens substrate14 is machined to form a V-shape groove 19, to form an aperture.

[0102] In this case also, similarly to the aspects shown in FIG. 6A andFIG. 7A, a portion of the light of the optical path of light incident onthe optical element 34 is reflected or refracted by the side faces ofthe V-shape groove 19 and bent in a direction other than the directionof the original optical path, so that the optical path is limited, andaction as an aperture can be obtained.

[0103] In the optical element (lens element) 35 of the aspect shown inFIG. 8B, the light incidence-side surface of the second lens substrate14 is machined to form two V-shape grooves 19 (19A, 19B), to form anaperture.

[0104] In this case also, similarly to the aspects shown in FIG. 6B andFIG. 7B, a portion of the light of the optical path of light incident onthe optical element 35 is reflected or refracted by the side faces ofthe two V-shape grooves 19A and 19B and is bent in a direction otherthan the direction of the original optical path, so that the opticalpath is limited, and action as an aperture can be obtained.

[0105] In the optical element (lens element) 36 of the aspect shown inFIG. 8C, the light incidence-side surface of the second lens substrate14 is cut obliquely by machining into an inclined surface 18, and bymeans of this inclined surface 18 an aperture is formed.

[0106] In this case also, similarly to the aspect shown in FIG. 7C, aportion of the light in the optical path of the light incident on theoptical element 36 is reflected or refracted by the inclined surface 18and is bent in a direction other than the direction of the originaloptical path, so that the optical path is limited, and action as anaperture can be obtained.

[0107] In the optical element (lens element) 37 shown in FIG. 8D, anopening portion is formed by machining of the light incidence-sidesurface of the second lens substrate 14 with the side face shaped as aninclined surface 20, the second objective lens 12 with higher refractiveindex than the second lens substrate 14 is exposed, and an aperture isformed by the inclined surface 20 of the side face of the openingportion.

[0108] In this case also, similarly to the aspect shown in FIG. 6C, theinclined surface 20 of the side face of the opening portion refracts orreflects a portion of the light of the optical path of light incident onthe optical element 37, and the light is bent in a direction other thanthe direction of the original optical path, so that the optical path islimited, and action as an aperture can be obtained.

[0109]FIG. 9A to FIG. 9C are cross-sectional views showing still otheraspects of an optical element of this invention.

[0110] In all aspects, the light emission-side surface of the secondlens substrate 14 is machined to form shielding means, that is, anaperture.

[0111] In the optical element (lens element) 38 of the aspect shown inFIG. 9A, the light emission-side surface of the second lens substrate 14is machined to form a V-shape groove 19, to form an aperture.

[0112] In this case also, similarly to the aspects shown in FIG. 6A,FIG. 7A and FIG. 8A, a portion of the light of the optical path of lightincident on the optical element 38 is reflected or refracted by the sidefaces of the V-shape groove 19 and bent in a direction other than thedirection of the original optical path, so that the optical path islimited, and action as an aperture can be obtained.

[0113] In the optical element (lens element) 39 of the aspect shown inFIG. 9B, the light emission-side surface of the second lens substrate 14is machined to form two V-shape grooves 19 (19A, 19B), to form anaperture.

[0114] In this case also, similarly to the aspects shown in FIG. 6B,FIG. 7B and FIG. 8B, a portion of the light of the optical path of lightincident on the optical element 39 is reflected or refracted by the sidefaces of the two V-shape grooves 19A and 19B and is bent in a directionother than the direction of the original optical path, so that theoptical path is limited, and action as an aperture can be obtained.

[0115] In the optical element (lens element) 40 of the aspect shown inFIG. 9C, the light emission-side surface of the second lens substrate 14is cut obliquely by machining into an inclined surface 18, and by meansof this inclined surface 18 an aperture is formed.

[0116] In this case also, similarly to the aspects shown in FIGS. 7C and8C, a portion of the light in the optical path of the light incident onthe optical element 40 is reflected or refracted by the inclined surface18 and is bent in a direction other than the direction of the originaloptical path, so that the optical path is limited, and action as anaperture can be obtained.

[0117] In place of forming an aperture by means of two grooves 19A and19B as shown in FIGS. 6B, 7B, 8B and 9B, an aperture may be formed byforming three or more grooves continuously in the horizontal direction.

[0118] Next, a method of formation of an aperture by means of theabsorptive or reflective film 15 shown in FIG. 1 to FIG. 3 is explained.FIG. 10 shows processes to manufacture an optical element comprising afirst lens substrate 13 on the light incidence-side surface of which isformed an absorptive or reflective film 15, as shown in FIG. 1.

[0119] As shown in FIG. 10A, first a structure is formed in which thereis embedded in a first lens substrate 13, comprising for example adielectric material, a first objective lens 11 of material with a higherrefractive index than the lens substrate 13.

[0120] Next, as shown in FIG. 10B, an ordinary photoresist process isused to pattern and form a resist film 51 in the portion of the lightincidence-side surface of the first lens substrate 13 through whichlight passes.

[0121] Next, as shown in FIG. 10C, ordinary sputtering or vacuumdeposition methods are used to deposit an absorptive or reflective film15 over the entire surface to a prescribed thickness.

[0122] As an absorptive film, for example, a layered film in whichsilicon oxide or another dielectric film is deposited to a prescribedthickness on top of chromium or another metal film, or a carbon or otherfilm with an extremely low reflectivity, can be used.

[0123] As a reflective film, ordinary metal such as aluminum, gold,chromium or similar can be used. Because there is no need for aparticularly high reflectivity, tungsten or another material with lowreflectivity may be used.

[0124] Finally, as shown in FIG. 10D, an ordinary lift-off method isused to remove the resist film 51 by immersion in acetone or anotherorganic solvent or resist-stripping material, and in addition theabsorptive or reflective film is also removed from on top of the resistfilm (the portion through which light passes).

[0125] In this way, an aperture comprising an absorptive or reflectivefilm 15 is completed.

[0126] In the configurations shown in FIG. 2 and FIG. 3 also, similarmanufacturing processes can be used to form an absorptive or reflectivefilm 15 on the lens substrate 13 or 14, to manufacture an opticalelement having an aperture formed from an absorptive or reflective film15.

[0127] Next, a method of forming an aperture using the portions whichdisperse light shown in FIG. 4, that is, the rough surface 17, isexplained. FIG. 11 shows manufacturing processes for the configurationshown in FIG. 4A in which the rough surface 17 is formed on the lightincidence-side surface of the first lens substrate 13.

[0128] As shown in FIG. 11A, first a structure is formed in which thereis embedded in a first lens substrate 13, comprising for example adielectric material, a first objective lens 11 of material with a higherrefractive index than the lens substrate 13.

[0129] Next, as shown in FIG. 11B, an ordinary photoresist process isused to pattern and form a resist film (polyimide film) 52 in theportion of the light incidence-side surface of the first lens substrate13 through which light passes.

[0130] Next, as shown in FIG. 11C, an ordinary sandblasting method isused to form the rough surface 17 in the portion of the lightincidence-side of the first lens substrate 13 not covered by the resistfilm 52.

[0131] Finally, as shown in FIG. 11D, an ordinary lift-off method isused to remove the resist film 52 by immersion in acetone or anotherorganic solvent or resist-stripping material.

[0132] In this way, an aperture formed by a rough surface 17 iscompleted.

[0133] The resist film 52 shown in FIG. 11B can use the same material ora different material from the material of the resist film 51 shownpreviously in FIG. 10B.

[0134] In the case of this FIG. 11, the sandblasting method results inconsiderable material removal, and so the resist film 52 is formed to athickness which anticipates this removal.

[0135] In the cases of the configurations shown in FIG. 4B and FIG. 4Calso, optical elements having an aperture formed by a rough surface 17can be manufactured by using similar manufacturing processes to form arough surface 17 on the lens substrate 13 or 14.

[0136] Next, a method of forming an aperture by means of a portion (aninclined surface 18, grooves 19, 19A, 19B, or the inclined surfaces 20of the side faces of an opening portion) which bends the course of lightutilizing the reflection or refraction of light as shown in FIG. 5through FIG. 9. Of these, manufacturing processes for a configuration inwhich a V-shape groove 19 is formed on the light incidence-side surfaceof the first lens substrate 13 in FIG. 6A are shown in FIG. 12.

[0137] As shown in FIG. 12A, first a structure is formed in which thereis embedded in a first lens substrate 13, comprising for example adielectric material, a first objective lens 11 of material with a higherrefractive index than the lens substrate 13.

[0138] Next, as shown in FIG. 12B, an ordinary photoresist process isused to pattern and form a resist film 54 in the portion of the lightincidence-side surface of the first lens substrate 13 excluding theportion in which a V-shape groove 19 is to be formed.

[0139] Next, as shown in FIG. 12C and FIG. 12D, an ordinary RIE(reactive ion etching) method or ion milling method is used to form aV-shape groove 19, by shaping the light incidence-side surface of thefirst lens substrate 13 using etching gas 55 or similar, with the resistfilm 54 employed as a mask. At this time, by inclining the substratewhich is rotating during etching, the V-shape groove 19 can easily beformed.

[0140] Finally, as shown in FIG. 12E, the resist film 54 is removed by amethod such as immersion in acetone or another organic solvent or in aresist stripping agent.

[0141] In this way, an aperture consisting of a V-shape groove 19 isformed.

[0142] In the cases of the configurations shown in FIG. 7A, FIG. 8A andFIG. 9A also, similar manufacturing processes can be used to form agroove 19 on the lens substrate 13 or 14, to manufacture an opticalelement having an aperture formed from the groove 19.

[0143] In the case of formation in the lens substrate 13 or 14 of anaperture consisting of two grooves 19A, 19B also, an RIE method or ionmilling method employing a mask can similarly be used to form the twogrooves 19A and 19B.

[0144] In this case, a resist film or other mask is formed outside theportion in which the two grooves 19A, 19B are to be formed and in thecenter of the two grooves 19A, 19B, and an RIE or ion milling method isused for shaping until the mask in the center of the two grooves 19A,19B is substantially removed.

[0145] In the case of formation in the lens substrate 13 or 14 of aninclined surface 18 by oblique cutting, either a method in which thesurface of the lens substrate 13 or 14 is shaped from the same state asin FIG. 10A, or a method in which material to become a lens is embeddedin a substrate 13 or 14 in a shape having an inclined surface 18 throughmold-shapeing in advance using a mold, can be adopted.

[0146] As in the configurations shown in FIG. 6C and FIG. 8D, when anopening portion the side walls of which are inclined surfaces 20 isformed in a lens substrate 13 or 14, a method like the following can,for example, by adopted.

[0147] For example, a depression for embedding of a lens is formed inthe lens substrate, and after forming a film of Al or similar on theinner surface of this depression to serve as an etching stopper, a lensof high-refractivity material is embedded in the lens substrate.

[0148] Then, a resist film or other mask is formed on the surface on theside on which the opening portion is to be formed, and similarly to FIG.12, the lens substrate is inclined and an RIE method, ion milling methodor similar is used to form the opening portion, the side face of whichis the inclined surface 20. At this time, cutting of the lens isprevented by the film serving as the etching stopper. For example, an Alfilm acts as an etching stopper with respect to flon and other etchinggases.

[0149] Thereafter, the etching stopper film and mask are removed. Forexample, an Al film can be removed using a KOH aqueous solution, an NaOHaqueous solution, phosphoric acid+water+acetic acid, and similar.

[0150] In the cases of the optical elements 31 to 40 of theabove-described aspects, by forming an aperture on the lightincidence-side or emission-side surface of the first or second lenssubstrate 13 or 14, an aperture very close to the optical elements 31 to40 can be formed.

[0151] By this means, even when optical axis inclination occurs in theincident light beam L due for example to movement in the horizontaldirection of the collimating lens 16, intrusion of the light beam L intounnecessary portions outside the effective area of the objective lenses11, 12 can be prevented by the aperture (15, 17, 18, 19, 20); and,inhibition of guidance of the light beam L into the region within theeffective area can be prevented.

[0152] Hence unstable oscillation, noise and similar problems due forexample to light returning to a semiconductor laser, resulting fromstray light intruding into unnecessary portions, can be avoided.

[0153] By using one of the optical elements 31 to 40 of theabove-described aspects to form an optical pickup comprising a lightsource such as a semiconductor laser, a beam splitter to separateoptical paths and other optical components, an optical pickup can beobtained in which noise is reduced and stable operation is achieved.

[0154] In each of the above-described aspects, this invention wasapplied to cases in which an objective lens was configured from twolenses, which are a first objective lens 11 and a second objective lens12 embedded respectively in two lens substrates 13 and 14; but thisinvention can be applied to other configurations as well.

[0155] For example, even when an optical element comprises only one lenssubstrate in which an objective lens of material with a high refractiveindex is embedded in a substrate, this invention can similarly beapplied, and shielding means, that is, an aperture, can be formed on thelight incidence-side or emission-side surface of the lens substrate.

[0156] And as shown for example in FIG. 13, this invention can also besimilarly applied to the case of an optical element (lens element) 10 inwhich two substrates 3, 4 are stacked, and an objective lens 2 ofhigh-refractivity material is embedded in only one of the substrates 3.

[0157] In this case, not only can shielding means, that is, an aperture,be formed on the light incidence-side or emission-side surface of thesubstrate 3 in which is embedded the objective lens 2, but shieldingmeans, that is, an aperture, can also be formed on the lightincidence-side or emission-side surface of the substrate 4 in which nolens is embedded.

[0158] Also, as for example proposed in Japanese Patent Application No.2000-132897, this invention can also be applied to a configuration inwhich still another lens is formed above a lens substrate in which isembedded a lens (a configuration in which there are one more lenses thanthere are substrates), and shielding means, that is, an aperture, can beformed on the light incidence-side or emission-side surface of a lenssubstrate.

[0159] This invention is not limited to the above-described aspects, andvarious other configurations can be adopted insofar as there is nodeviation from the essence of this invention.

[0160] By means of the above-described invention, shielding means (anaperture) can be formed very close to an objective lens, so that even iffor example inclination of the optical axis of incident light occurs,intrusion of light into unwanted portions can be prevented by theshielding means, and inhibition of guidance of light into the regionwithin the effective area can be prevented.

[0161] Hence unstable oscillation, noise and similar problems due forexample to light returning to a semiconductor laser, resulting fromstray light intruding into unnecessary portions, can be avoided.

1. An optical element, comprising one or more substrates transparent toincident light, comprising a lens substrate formed by embedding, in asubstrate transparent to incident light, a lens of material withrefractive index higher than said substrate; characterized in thatshielding means to limit the optical path such that incident lightpropagates only within a prescribed optical path, by the action ofreflection, refraction, absorption, or dispersion, is formed on thesurface on which said light is incident or is emitted of any one of thesubstrates among said one or more substrates.
 2. The optical elementaccording to claim 1, characterized in being configured by stacking aplurality of said lens substrates.
 3. A manufacturing method for opticalelements, in which an optical element is formed comprising one or moresubstrates transparent to incident light, comprising a lens substrateformed by embedding, in a substrate transparent to incident light, alens of material with refractive index higher than said substrate;characterized in having a process in which an absorptive or reflectivefilm is formed in a region outside a prescribed optical path on thelight incidence-side surface or emission-side surface of any one amongsaid one or more substrates.
 4. A manufacturing method for opticalelements, in which an optical element is formed comprising one or moresubstrates transparent to incident light, comprising a lens substrateformed by embedding, in a substrate transparent to incident light, alens of material with refractive index higher than said substrate;characterized in having a process in which a region outside a prescribedoptical path on the light incidence-side surface or emission-sidesurface of any one among said one or more substrates is shaped ormachined.
 5. The manufacturing method for optical elements according toclaim 4, characterized in that said process to shape or machine a regionoutside a prescribed optical path is a process of forming a roughsurface in the region.
 6. The manufacturing method for optical elementsaccording to claim 4, characterized in that said process to shape ormachine a region outside a prescribed optical path is a process ofmachining into an inclined surface in the region.
 7. The manufacturingmethod for optical elements according to claim 4, characterized in thatsaid process to shape or machine a region outside a prescribed opticalpath is a process of forming a groove in the region.
 8. Themanufacturing method for optical elements according to claim 4,characterized in that said process to shape or machine a region outsidea prescribed optical path is a process of opening said region and theregion in the prescribed optical path to form an opening portion.